Monitoring of tire pressure can be assumed to become a standard functionality in vehicles, at least in cars and trucks, not only due to governmental and legal regulations but also in view of a general demand for enhanced vehicle safety.
The importance of having correct tire inflation pressure is well known. The inflation pressure directly affects, e.g., the vehicle handling, the load capacity, and the fuel consumption. There are studies that indicate that tire related problems are the third most common reason for breakdown of passenger vehicles. Furthermore, it has been shown that a majority of all tire flat-outs is preceded by under-inflation or slow air leakage. With tire pressure monitoring that detects the presence of air leakages, severe accidents can thus be avoided.
Besides these well known facts about the importance of having a correct inflation pressure, tire pressure monitoring has become even more important since legal regulations in some countries require all new motor vehicles to be equipped with a system that monitors the tire pressure.
There are two alternative approaches to monitor the tire pressure. One way is to mount a pressure sensor inside the tire and transfer the pressure sensor value wireless to an on-board tire pressure system of the vehicle. This approach is referred to as “direct tire pressure monitoring”. The other alternative, called “indirect tire pressure monitoring”, uses existing sensors (e.g. control and/or detection devices of vehicles, ECUs (electronic control unit), antilock braking systems, dynamic stability systems, anti-spin systems and traction control systems, in form of digital and/or analog data and/or signals) to compute quantities related to the tire pressure. Indirect tire pressure monitoring is not directly measuring the air/gas pressure in a tire. Rather, parameters correlated with tire pressure are calculated using data available from the vehicle (e.g. from brake system or the electronic stability control system) and, on the basis of such parameters, tire pressure is indicated.
Vehicle data commonly used in tire pressure monitoring is data indicating an effective roll radius of wheel/tire. For the sake of illustration, it will be referred to such wheel radius data in the following.
However, there are several effects possibly influencing actual tire pressure and, thus, relation(s) between actual tire pressure and data from which actual tire pressure, an estimation thereof or tire pressure deviation is to be derived.
For example, current driving situations (e.g. acceleration, deceleration; driving on smooth road surfaces vs. rough road surfaces; driving in curves etc.), temperature(s) affecting tire pressure and the like may influence actual tire pressure and should be therefore take into account in indirect tire pressure monitoring.
Further, different tire types will have different properties that may be also taken into account in indirect tire pressure monitoring. For example, different tires (brand, dimension, winter/summer, etc.) to some extent respond differently to changes in inflation pressure, e.g., for a given amount of tire pressure loss, a corresponding change in e.g. effective roll radius will differ between different tires. To ensure a reliable indirect tire pressure monitoring a consistent behavior in general, it would be helpful to specify the behavior of the pressure related parameters of tire(s).
To this end, an approach may be performing in-vehicle tests where a vehicle equipped with a tire type of interest is actually driven, wherein, e.g., pressure related tire behavior may be specified. However, such an approach will be time-consuming and expensive.